Lithium secondary battery comprising a negative electrode consisting essentially of B2 O3

ABSTRACT

Provided is a lithium secondary battery which has a large discharge capacity and good charge-discharge cycle characteristics comprising a negative electrode in which the lithium ion-occlusion material is an amorphous material consisting essentially of B 2  O 3  or an amorphous material consisting essentially of B 2  O 2  and an oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole.

BACKGROUND OF THE INVENTION

This application claims the priority of Japanese Patent Application No. 9-210113 filed on Jul. 17, 1997.

1. Field of the Invention

The present invention relates to a lithium secondary battery which comprises a positive electrode, a negative electrode comprising a lithium ion-occlusion material and a nonaqueous electrolyte and, more particularly to improvements in the lithium ion-occlusion material to be used in the negative electrode for the purpose of providing a lithium secondary battery having a large discharge capacity and good charge-discharge cycle characteristics.

2. Description of the Prior Art

Carbonaceous materials are well known as lithium ion-occlusion materials to be used in the negative electrode of lithium secondary batteries.

However, since carbonaceous materials have conductivity, overcharge may possibly result in ramiform deposition of metallic lithium on the surface thereof. Therefore, when a carbonaceous material is used, it is necessary to prevent overcharge of the carbonaceous material by decreasing the capacity of the positive electrode and/or using a charger provided with an overcharge preventing function, for instance.

Therefore, oxides of elements of the group IVB or VB of the periodic table, for example oxides of Ge, Sn and so on, have been proposed as lithium ion-occlusion materials for negative electrodes substituting for the carbonaceous materials (cf. Japanese Kokai Tokkyo Koho H07-122274). It is stated that by using these oxides, it is possible to obtain secondary batteries which have a relatively large discharge capacity and do not cause ramiform deposition of metallic lithium on the surface of the negative electrode even upon overcharge.

However, check experiments made by the present inventors revealed that when these oxides are used as lithium ion-occlusion materials for negative electrodes, the oxide structure rapidly undergoes destruction upon repeated charge and discharge, namely repeated lithium ion incorporation and elimination, whereby the discharge capacity decreases in a small number of charge-discharge cycles. Thus, it was revealed that the secondary batteries disclosed in Japanese Kokai Tokkyo Koho H07-122274 have a problem in terms of charge-discharge cycle characteristics.

Accordingly, it is an object of the present invention to provide a lithium secondary battery having a large discharge capacity and good charge-discharge cycle characteristics.

SUMMARY OF THE INVENTION

In the present invention, an amorphous material comprising a specific oxide is used as the lithium ion-occlusion material for the negative electrode in lieu of the oxides of group IVB or VB elements in order to achieve the above object. Thus, a lithium secondary battery (first battery) according to the present invention comprises a positive electrode, a negative electrode in which the lithium ion-occlusion material is an amorphous material consisting essentially of B₂ O₃ (diboron trioxide), and a nonaqueous electrolyte. Another lithium secondary battery (second battery) according to the present invention comprises a positive electrode, a negative electrode in which the lithium ion-occlusion material is an amorphous material consisting essentially of B₂ O₃ and an oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole, and a nonaqueous electrolyte. In this specification, the first and second batteries are sometimes collectively referred to as "the batteries of the present invention."

In the first battery, an amorphous material consisting essentially of B₂ O₃ is used as the lithium ion-occlusion material. This amorphous material can be prepared, for example, by heating B₂ O₃ for melting, followed by cooling. The cation-oxygen bond strength of B₂ O₃ is more than 335 kJ/mole and this oxide can readily form an amorphous material. Since it is a component forming an irregular three-dimensional network structure of glass, it is called a network-forming oxide or glass-forming oxide. There are other network-forming oxides, such as GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ and V₂ O₅. However, these other network-forming oxides cannot give lithium secondary batteries having good characteristics.

In the second battery, an amorphous material consisting essentially of B₂ O₃ and an oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole is used as the lithium ion-occlusion material. This amorphous material can be prepared by heating and melting B₂ O₃ and an oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole, followed by cooling. As the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole, there may be mentioned modifier oxides such as MoO₂ (cation-oxygen bond strength<250 kJ/mole), WO₃ (bond strength<250 kJ/mole), W₂ O₅, (bond strength<250 kJ/mole), Bi₂ O₃ (bond strength<250 kJ/mole), Sc₂ O₃ (bond strength=250 kJ/mole), La₂ O₃ (bond strength=242 kJ/mole), Y₂ O₃ (bond strength=209 kJ/mole), MgO (bond strength=155 kJ/mole), Li₂ O (bond strength=151 kJ/mole), BaO (bond strength=138 kJ/mole), CaO (bond strength=134 kJ/mole), SrO (bond strength=134 kJ/mole), Na₂ O (bond strength=84 kJ/mole) and K₂ O (bond strength=54 kJ/mole) as well as intermediate oxides such as PbO (bond strength=180 kJ/mole), ZnO (bond strength=180 kJ/mole), CdO (bond strength=251 kJ/mole), TiO₂ (bond strength=305 kJ/mole), ZrO₂ (bond strength=255 kJ/mole) and Al₂ O₃ (bond strength=222 kJ/mole). The modifier oxides enter the networks formed by network-forming oxides and modify the properties of amorphous materials. The intermediate oxides by themselves cannot form amorphous materials but have simultaneously a role as network-forming oxides as resulting from their cation slightly substituting for B³⁺ to partially participating the networks and a role as modifier oxides. A modifier oxide and an intermediate oxide may both be used as the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole. The modifier oxides and intermediate oxides such as mentioned above may be used respectively singly or, where necessary, two or more may be selected from the respective groups.

The amorphous material to be used as the lithium ion-occlusion material in the second battery is preferably composed of 1 mole part of B₂ O₃, and not more than 9 mole parts of an oxide whose cation-oxygen bond strength is smaller than 335 k J/mole. When the proportion of the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole is too excessive, a decreased discharge capacity and poor charge-discharge cycle characteristics will result.

The present invention relates to improvements of the lithium ion-occlusion materials for negative electrodes of lithium secondary batteries. Therefore, as regards other battery-constituting parts and elements, those conventional materials known for lithium secondary batteries can be used without any limitation.

As examples of the positive electrode active material, there may be mentioned lithium-transition metal composite oxide, such as LiCoO₂, LiNiO₂, LiFeO₂, LiTiO₂ and LiMn₂ O₄.

As examples of the solvent in the nonaqueous electrolyte solution, there may be mentioned cyclic carbonate such as ethylene carbonate (EC), propylene carbonate (PC), vinylene carbonate (VC) and butylene carbonate (BC) as well as mixed solvents composed of such a cyclic carbonate and a low-boiling solvent such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), 1,2-dimethoxyethane (DME), 1,2-diethoxyethane (DEE) and ethoxymethoxyethane (EME). As examples of the solute (electrolyte salt) in the nonaqueous electrolyte solution, there may be mentioned LiPF₆, LiAsF₆, LiSbF₆, LiBF₄ and LiClO₄. Solid electrolytes may also be used.

The battery of the present invention has a large discharge capacity and good charge-discharge cycle characteristics. The reason why its charge-discharge cycle characteristics are good is not certain but may presumably be that since B₂ O₃ used as the lithium ion-occlusion material of the negative electrode is an amorphous material having a stable three-dimensional network structure, repetitions of lithium incorporation and elimination can hardly lead to destruction of the structure.

EXAMPLES

The following examples illustrate the present invention in further detail but are by no means limitative of the scope of the invention. Various modifications may be made without departing from the spirit and scope thereof.

Experiment 1

In this experiment, first battery A1 in which the lithium ion-occlusion material was an amorphous material consisting of a network-forming oxide, and a comparative battery AC1 in which the lithium ion-occlusion material was an amorphous material consisting of a modifier oxide were fabricated and each was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Fabrication of first battery A1

The positive electrode, negative electrode and nonaqueous electrolyte solution were prepared as described below and, using these, first battery A1 (AA-size) was fabricated. The capacity ratio between positive electrode and negative electrode was 1:1.1. A microporous polypropylene membrane was used as the separator. The battery size was 18 mm in diameter and 65 mm in height.

Preparation of positive electrode

A slurry was prepared by kneading 90 weight parts of LiCoO₂, 6 weight parts of acetylene black (conductive agent) and an N-methyl-2-pyrrolidone (NMP) solution of 4 weight parts of polyvinylidene fluoride. This slurry was applied to both sides of an aluminum foil (current collector) by the doctor blade method. The subsequent drying under vacuum at 100° C. for 2 hours gave a positive electrode.

Preparation of negative electrode

B₂ O₃ (network-forming oxide) was melted by heating at 1,000° C. in a nitrogen gas atmosphere, then gradually cooled at a rate of 10° C./minute, and ground to give a glass powder (amorphous material) consisting of B₂ O₃ with a mean particle size of 10 μm. The fact that X-ray diffraction analysis (XRD) gave no peak confirmed that this powder was a glass powder. A slurry was prepared by kneading 90 weight parts of this glass powder (lithium ion-occlusion material), 5 weight parts of natural graphite (conductive agent) and an N-methyl-2-pyrrolidone (NMP) solution of 5 weight parts of polyvinylidene fluoride. This slurry was applied to both sides of a copper foil (current collector) by the doctor blade method, The subsequent drying under vacuum at 100° C. for 2 hours gave a negative electrode.

Preparation of nonaqueous electrolyte solution

A nonaqueous electrolyte solution was prepared by dissolving LiPF₆ in a mixed solvent composed of ethylene carbonate and diethyl carbonate (volume ratio 1:1) to a concentration of 1 mole/liter.

Fabrication of comparative battery AC1

A comparative battery AC1 was fabricated in the same manner as in the fabrication of first battery A1 except that SnO (modifier oxide) was used in lieu of B₂ O₃ in preparing the negative electrode.

Discharge capacity of each battery in the first cycle and capacity maintenance thereof in the 500th cycle

Each battery was subjected to charge-discharge cycle testing. Each cycle consisted of charging to 4.2 V at a constant current of 1,000 mA and discharging to 2.75 V at a constant current of 1,000 mA. Each battery was evaluated for its discharge capacity (mAh) in the first cycle and for the capacity maintenance (%) in the 500th cycle as defined below. The results are shown in Table 1.

Capacity maintenance (%)=(discharge capacity in 500th cycle/discharge capacity in 1st cycle)×100

                  TABLE 1                                                          ______________________________________                                                 Network-      Discharge                                                                               Capacity                                           forming Capacity Maintenance                                                  Battery Oxide (mAh) (%)                                                      ______________________________________                                         A1      B.sub.2 O.sub.3                                                                              1900     90                                                AC1 SnO 1700 10                                                              ______________________________________                                    

As shown in Table 1, the capacity maintenance in the 500th cycle of first battery A1 was as high as 90% while the capacity maintenance of comparative battery AC1 was as low as 10%. This fact indicates that first battery A1 is decidedly superior in charge-discharge cycle characteristics to comparative battery AC1. Furthermore, first battery A1 shows a larger discharge capacity as compared with comparative battery AC1.

Experiment 2

In this experiment, second batteries B1 to B14 in which the lithium ion-occlusion material was an amorphous material composed of a network-forming oxide and a modifier oxide, and comparative batteries BC1 to BC14 in which the lithium ion-occlusion material was an amorphous material composed of two modifier oxides were fabricated and each was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Fabrication of second batteries B1 to B14

A mixture of B₂ O₃ and one of the modifier oxides shown in Table 2 in a molar ratio of 2:1 was melted by heating at 1,000° C. in a nitrogen gas atmosphere, then cooled gradually at a rate of 10° C./minute, and ground to give a glass powder (amorphous material) with a mean particle size of 10 μm. Second batteries B1 to B14 were fabricated in the same manner as in the fabrication of first battery A1 except that this glass powder was used in the preparation of the negative electrode.

Fabrication of comparative batteries BC1 to BC14

Comparative batteries BC1 to BC14 were fabricated in the same manner as in the fabrication of second batteries B1 to B14 except that a mixture of SnO and one of the modifier oxides shown in Table 2 in a molar ratio of 2:1 was used in the preparation of the negative electrode in lieu of the mixture of B₂ O₃ and one of the modifier oxides shown in table 2.

Each of the above batteries was subjected to charge-discharge cycle testing under the same conditions as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results are shown in Table 2.

                  TABLE 2                                                          ______________________________________                                                  Network-           Discharge                                                                               Capacity                                     forming Modifier Capacity Maintenance                                         Battery Oxide Oxide (mAh) (%)                                                ______________________________________                                         B1       B.sub.2 O.sub.3                                                                          Sc.sub.2 O.sub.3                                                                        1950     90                                          B2  B.sub.2 O.sub.3 La.sub.2 O.sub.3 1900 88                                   B3  B.sub.2 O.sub.3 Y.sub.2 O.sub.3 1910 91                                    B4  B.sub.2 O.sub.3 MgO 2000 85                                                B5  B.sub.2 O.sub.3 Li.sub.2 O 1900 88                                         B6  B.sub.2 O.sub.3 BaO 2010 87                                                B7  B.sub.2 O.sub.3 CaO 1950 88                                                B8  B.sub.2 O.sub.3 SrO 1850 83                                                B9  B.sub.2 O.sub.3 Na.sub.2 O 1820 84                                         B10  B.sub.2 O.sub.3 K.sub.2 O 1850 83                                         B11  B.sub.2 O.sub.3 MoO.sub.2 1830 86                                         B12  B.sub.2 O.sub.3 WO.sub.3 1950 87                                          B13  B.sub.2 O.sub.3 W.sub.2 O.sub.5 2050 90                                   B14  B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 1850 89                                  BC1  SnO Sc.sub.2 O.sub.3 1600  8                                              BC2  SnO La.sub.2 O.sub.3 1640 15                                              BC3  SnO Y.sub.2 O.sub.3 1650 13                                               BC4  SnO MgO 1670  9                                                           BC5  SnO Li.sub.2 O 1650 18                                                    BC6  SnO BaO 1660 15                                                           BC7  SnO CaO 1620 14                                                           BC8  SnO SrO 1590 17                                                           BC9  SnO Na.sub.2 O 1570 16                                                    BC10 SnO K.sub.2 O 1550  8                                                     BC11 SnO MoO.sub.2 1610 16                                                     BC12 SnO WO.sub.3 1630 15                                                      BC13 SnO W.sub.2 O.sub.5 1630 11                                               BC14 SnO Bi.sub.2 O.sub.3 1670  9                                            ______________________________________                                    

As shown in Table 2, second batteries B1 to B14 showed capacity maintenances as high as 83 to 91% in the 500th cycle whereas comparative batteries BC1 to BC14 showed capacity maintenances as low as 8 to 18% in the 500th cycle. This fact indicates that secondary batteries B1 to B14 are much better in charge-discharge cycle characteristics than comparative batteries BC1 to BC14. Furthermore, secondary batteries B1 to B14 showed larger discharge capacities as compared with comparative batteries BC1 to BC14.

Experiment 3

In this experiment, second batteries B15 to B20 in which the lithium ion-occlusion material was an amorphous material composed of a network-forming oxide and an intermediate oxide, and comparative batteries BC15 to BC20 in which the lithium ion-occlusion material was an amorphous material composed of a modifier oxide and an intermediate oxide were fabricated and each was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Fabrication of second batteries B15 to B20

A mixture of B₂ O₃ and one of the intermediate oxides shown in Table 3 in a molar ratio of 2:1 was melted by heating at 1,000° C. in a nitrogen gas atmosphere, then cooled gradually at a rate of 10° C./minute, and ground to give a glass powder (amorphous material) with a mean particle size of 10 μm. Second batteries B15 to B20 were fabricated in the same manner as in the fabrication of first battery A1 except that each glass powder obtained in the above manner was used in the preparation of the negative electrode.

Fabrication of comparative batteries BC15 to BC20

Comparative batteries BC15 to BC20 were fabricated in the same manner as in the fabrication of second batteries B15 to B20 except that, in the preparation of the negative electrode, a mixture of SnO and one of the intermediate oxides shown in Table 3 in a molar ratio of 2:1 was used in lieu of the mixture of B₂ O₃ and one of the intermediate oxides shown in Table 3 in a molar ratio of 2:1.

The above batteries were each subjected to charge-discharge cycle testing under the same conditions as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results are shown in Table 3.

                  TABLE 3                                                          ______________________________________                                                Network-             Discharge                                                                             Capacity                                       forming Intermediate Capacity Maintenance                                     Battery Oxide Oxide (mAh) (%)                                                ______________________________________                                         B15    B.sub.2 O.sub.3                                                                          PbO        1950   90                                            B16  B.sub.2 O.sub.3 ZnO 1900 88                                               B17  B.sub.2 O.sub.3 TiO.sub.2 1910 91                                         B18  B.sub.2 O.sub.3 ZrO.sub.2 2000 85                                         B19  B.sub.2 O.sub.3 CdO 1900 88                                               B20  B.sub.2 O.sub.3 Al.sub.2 O.sub.3 2010 87                                  BC15 SnO PbO 1600  8                                                           BC16 SnO ZnO 1640 15                                                           BC17 SnO TiO.sub.2 1650 13                                                     BC18 SnO ZrO.sub.2 1670  9                                                     BC19 SnO CdO 1650 18                                                           BC20 SnO Al.sub.2 O.sub.3 1660 15                                            ______________________________________                                    

As shown in Table 3, second batteries B15 to B20 showed high capacity maintenances of 85 to 91% in the 500th cycle whereas comparative batteries BC15 to BC20 showed very low capacity maintenances of 8 to 18% in the 500th cycle. This fact indicates that second batteries B15 to B20 are decidedly superior in charge-discharge cycle characteristics to comparative batteries BC15 to BC20. Furthermore, second batteries B15 to B20 showed larger discharge capacities as compared with comparative batteries BC15 to BC20.

Experiment 4

In this experiment, second batteries B21 to B38 in which the lithium ion-occlusion material was an amorphous material composed of a network-forming oxide, a modifier oxide and an intermediate oxide, and comparative batteries BC21 to BC38 in which the lithium ion-occlusion material was an amorphous material composed of two modifier oxides and an intermediate oxide were fabricated and each battery was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Fabrication of second batteries B21 to B38

A mixture of B₂ O₃ and the modifier oxide and intermediate oxide specified in Table 4 or 5 in a molar ratio of 2:1:1 was melted by heating at 1,000° C. in a nitrogen gas atmosphere, then cooled gradually at a rate of 10° C./minute, and ground to give a glass powder (amorphous material) with a mean particle size of 10 μm. Second batteries B21 to B38 were fabricated in the same manner as in the fabrication of first battery A1 except that each glass powder thus obtained was used in the preparation of the negative electrode.

Fabrication of comparative batteries BC21 to BC38

Comparative batteries BC21 to BC38 were fabricated in the same manner as in the fabrication of second batteries B21 to B38 except that, in the negative electrode preparation, a mixture of SnO and the modifier oxide and intermediate oxide specified in Table 4 or 5 in a molar ratio of 2:1:1 was used in lieu of the mixture of B₂ O₃ and the modifier oxide and intermediate oxide specified in Table 4 or 5 in a molar ratio of 2:1:1.

Each battery was subjected to charge-discharge cycle testing in the same manner as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results thus obtained are shown in Table 4 and Table 5.

                  TABLE 4                                                          ______________________________________                                               Network-                  Discharge                                                                             Capacity                                   forming Modifier Intermediate Capacity Maintenance                            Battery Oxide Oxide Oxide (mAh) (%)                                          ______________________________________                                         B21   B.sub.2 O.sub.3                                                                         W.sub.2 O.sub.5                                                                         PbO     1950   90                                        B22  B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZnO 1900 88                               B23  B.sub.2 O.sub.3 W.sub.2 O.sub.5 TiO.sub.2 1910 91                         B24  B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZrO.sub.2 2000 85                         B25  B.sub.2 O.sub.3 W.sub.2 O.sub.5 CdO 1900 88                               B26  B.sub.2 O.sub.3 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 2010 87                  BC21 SnO W.sub.2 O.sub.5 PbO 1600  8                                           BC22 SnO W.sub.2 O.sub.5 ZnO 1640 15                                           BC23 SnO W.sub.2 O.sub.5 TiO.sub.2 1650 13                                     BC24 SnO W.sub.2 O.sub.5 ZrO.sub.2 1670  9                                     BC25 SnO W.sub.2 O.sub.5 CdO 1650 18                                           BC26 SnO W.sub.2 O.sub.5 Al.sub.2 O.sub.3 1660 15                              B27  B.sub.2 O.sub.3 MoO.sub.2 PbO 1900 90                                     B28  B.sub.2 O.sub.3 MoO.sub.2 ZnO 1850 88                                     B29  B.sub.2 O.sub.3 MoO.sub.2 TiO.sub.2 1860 91                               B30  B.sub.2 O.sub.3 MoO.sub.2 ZrO.sub.2 1960 85                               B31  B.sub.2 O.sub.3 MoO.sub.2 CdO 1830 88                                     B32  B.sub.2 O.sub.3 MoO.sub.2 Al.sub.2 O.sub.3 2000 87                        BC27 SnO MoO.sub.2 PbO 1400  8                                                 BC28 SnO MoO.sub.2 ZnO 1340 15                                                 BC29 SnO MoO.sub.2 TiO.sub.2 1250 13                                           BC30 SnO MoO.sub.2 ZrO.sub.2 1370  9                                           BC31 SnO MoO.sub.2 CdO 1350 18                                                 BC32 SnO MoO.sub.2 Al.sub.2 O.sub.3 1360 15                                  ______________________________________                                    

                  TABLE 5                                                          ______________________________________                                               Network-                  Discharge                                                                             Capacity                                   forming Modifier Intermediate Capacity Maintenance                            Battery Oxide Oxide Oxide (mAh) (%)                                          ______________________________________                                         B33   B.sub.2 O.sub.3                                                                         Bi.sub.2 O.sub.3                                                                        PbO     1910   90                                        B34  B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZnO 1860 88                              B35  B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 TiO.sub.2 1880 91                        B36  B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZrO.sub.2 1900 85                        B37  B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 CdO 1870 88                              B38  B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 Al.sub.2 O.sub.3 2020 87                 BC33 SnO Bi.sub.2 O.sub.3 PbO 1430  8                                          BC34 SnO Bi.sub.2 O.sub.3 ZnO 1370 15                                          BC35 SnO Bi.sub.2 O.sub.3 TiO.sub.2 1340 14                                    BC36 SnO Bi.sub.2 O.sub.3 ZrO.sub.2 1400  9                                    BC37 SnO Bi.sub.2 O.sub.3 CdO 1350 18                                          BC38 SnO Bi.sub.2 O.sub.3 Al.sub.2 O.sub.3 1390 15                           ______________________________________                                    

As shown in Table 4 and Table 5, second batteries B21 to B38 showed high capacity maintenances as high as 85 to 91% in the 500th cycle, whereas comparative batteries BC21 to BC38 showed very low capacity maintenances of 8 to 18% in the 500th cycle. This fact indicates that second batteries B21 to B38 are decidedly superior in charge-discharge cycle characteristics to comparative batteries BC21 to BC38. Furthermore, second batteries B21 to B38 showed larger discharge capacities as compared with comparative batteries BC21 to BC38.

Experiment 5

In this experiment, second batteries B39 to B94 in which the lithium ion-occlusion material was an amorphous material composed of a network-forming oxide and a modifier oxide as well as second batteries B95 to B166 in which the lithium ion-occlusion material was an amorphous material composed of a network-forming oxide, a modifier oxide and an intermediate oxide were fabricated. Based on the data on discharge capacities and on 500th cycle capacity maintenances as obtained with these batteries, an optimal content of the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole to be contained in the amorphous material for use in the seconds battery was determined.

Fabrication of second batteries B39 to B94

A mixture of B₂ O₃ and one of the modifier oxides shown in Table 6 or Table 7 in a molar ratio of 1;1, 3:7, 1:9 or 9:91 was melted by heating at 1,000° C. in a nitrogen gas atmosphere, then cooled gradually at a rate of 10° C./minute, and ground to give a glass powder (amorphous material) with a mean particle size of 10 μm. Second batteries B39 to B94 were fabricated in the same manner as in the fabrication of first battery A1 except that each glass powder obtained in the above manner was used in the preparation of the negative electrode.

Fabrication of second batteries B95 to B166

A mixture of B₂ O₃ and the modifier oxide and intermediate oxide shown in Table 8, Table 9 or Table 10 in a molar ratio of 1:1 1, 1:2:2, 2:9:9 or 9:45:46 was melted by heating at 1,000° C. in a nitrogen gas atmosphere, then cooled gradually at a rate of 10° C./minute, and ground to give a glass powder (amorphous material) with a mean particle size of 10 μm. Second batteries B95 to B166 were fabricated in the same manner as in the fabrication of first battery A1 except that each glass powder obtained in the above manner was used in the preparation of the negative electrode.

Each battery was subjected to charge-discharge cycle testing under the same conditions as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results are shown in Tables 6 to 10.

                  TABLE 6                                                          ______________________________________                                                Network-                                                                   forming Modifier Molar Discharge Capacity                                      Oxide Oxide Ratio Capacity Maintenance                                        Battery X Y X:Y (mAh) (%)                                                    ______________________________________                                         B39    B.sub.2 O.sub.3                                                                         Sc.sub.2 O.sub.3                                                                        1:1    1940   91                                        B40 B.sub.2 O.sub.3 Sc.sub.2 O.sub.3 3:7 1945 92                               B41 B.sub.2 O.sub.3 Sc.sub.2 O.sub.3 1:9 1940 90                               B42 B.sub.2 O.sub.3 Sc.sub.2 O.sub.3  9:91 1850 80                             B43 B.sub.2 O.sub.3 La.sub.2 O.sub.3 1:1 1905 89                               B44 B.sub.2 O.sub.3 La.sub.2 O.sub.3 3:7 1899 88                               B45 B.sub.2 O.sub.3 La.sub.2 O.sub.3 1:9 1897 87                               B46 B.sub.2 O.sub.3 La.sub.2 O.sub.3  9:91 1730 75                             B47 B.sub.2 O.sub.3 Y.sub.2 O.sub.3 1:1 1910 91                                B48 B.sub.2 O.sub.3 Y.sub.2 O.sub.3 3:7 1905 90                                B49 B.sub.2 O.sub.3 Y.sub.2 O.sub.3 1:9 1911 92                                B50 B.sub.2 O.sub.3 Y.sub.2 O.sub.3  9:91 1800 81                              B51 B.sub.2 O.sub.3 MgO 1:1 2000 85                                            B52 B.sub.2 O.sub.3 MgO 3:7 1999 86                                            B53 B.sub.2 O.sub.3 MgO 1:9 1995 83                                            B54 B.sub.2 O.sub.3 MgO  9:91 1910 71                                          B55 B.sub.2 O.sub.3 Li.sub.2 O 1:1 1900 88                                     B56 B.sub.2 O.sub.3 Li.sub.2 O 3:7 1899 89                                     B57 B.sub.2 O.sub.3 Li.sub.2 O 1:9 1901 87                                     B58 B.sub.2 O.sub.3 Li.sub.2 O  9:91 1801 75                                   B59 B.sub.2 O.sub.3 BaO 1:1 2011 89                                            B60 B.sub.2 O.sub.3 BaO 3:7 2015 86                                            B61 B.sub.2 O.sub.3 BaO 1:9 2009 88                                            B62 B.sub.2 O.sub.3 BaO  9:91 1905 76                                          B63 B.sub.2 O.sub.3 CaO 1:1 1950 88                                            B64 B.sub.2 O.sub.3 CaO 3:7 1955 89                                            B65 B.sub.2 O.sub.3 CaO 1:9 1937 87                                            B66 B.sub.2 O.sub.3 CaO  9:91 1805 77                                        ______________________________________                                    

                  TABLE 7                                                          ______________________________________                                                Network-                                                                   forming Modifier Molar Discharge Capacity                                      Oxide Oxide Ratio Capacity Maintenance                                        Battery X Y X:Y (mAh) (%)                                                    ______________________________________                                         B67    B.sub.2 O.sub.3                                                                         SrO      1:1    1856   82                                        B68 B.sub.2 O.sub.3 SrO 3:7 1855 83                                            B69 B.sub.2 O.sub.3 SrO 1:9 1849 84                                            B70 B.sub.2 O.sub.3 SrO  9:91 1745 73                                          B71 B.sub.2 O.sub.3 Na.sub.2 O 1:1 1821 85                                     B72 B.sub.2 O.sub.3 Na.sub.2 O 3:7 1822 84                                     B73 B.sub.2 O.sub.3 Na.sub.2 O 1:9 1825 83                                     B74 B.sub.2 O.sub.3 Na.sub.2 O  9:91 1701 72                                   B75 B.sub.2 O.sub.3 K.sub.2 O 1:1 1849 83                                      B76 B.sub.2 O.sub.3 K.sub.2 O 3:7 1850 82                                      B77 B.sub.2 O.sub.3 K.sub.2 O 1:9 1853 85                                      B78 B.sub.2 O.sub.3 K.sub.2 O  9:91 1745 71                                    B79 B.sub.2 O.sub.3 MoO.sub.2 1:1 1832 87                                      B80 B.sub.2 O.sub.3 MoO.sub.2 3:7 1835 85                                      B81 B.sub.2 O.sub.3 MoO.sub.2 1:9 1830 84                                      B82 B.sub.2 O.sub.3 MoO.sub.2  9:91 1740 75                                    B83 B.sub.2 O.sub.3 WO.sub.3 1:1 1951 87                                       B84 B.sub.2 O.sub.3 WO.sub.3 3:7 1955 86                                       B85 B.sub.2 O.sub.3 WO.sub.3 1:9 1950 86                                       B86 B.sub.2 O.sub.3 WO.sub.3  9:91 1855 73                                     B87 B.sub.2 O.sub.3 W.sub.2 O.sub.5 1:1 2051 90                                B88 B.sub.2 O.sub.3 W.sub.2 O.sub.5 3:7 2045 91                                B89 B.sub.2 O.sub.3 W.sub.2 O.sub.5 1:9 2051 90                                B90 B.sub.2 O.sub.3 W.sub.2 O.sub.5  9:91 1951 81                              B91 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 1:1 1850 88                               B92 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 3:7 1853 87                               B93 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 1:9 1850 89                               B94 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3  9:91 1743 78                           ______________________________________                                    

                                      TABLE 8                                      __________________________________________________________________________          Network-                                                                     forming Modifier Intermediate Molar Discharge Capacity                         Oxide Oxide Oxide Ratio Capacity Maintenance                                  Battery X Y Z X:Y:Z (mAh) (%)                                                __________________________________________________________________________     B95  B.sub.2 O.sub.3                                                                      W.sub.2 O.sub.5                                                                      PbO   1:1:1                                                                               1950 90                                              B96  B.sub.2 O.sub.3 W.sub.2 O.sub.5 PbO 1:2:2 1949 91                         B97  B.sub.2 O.sub.3 W.sub.2 O.sub.5 PbO 2:9:9 1940 90                         B98  B.sub.2 O.sub.3 W.sub.2 O.sub.5 PbO 9:45:46 1830 78                       B99  B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZnO 1:1:1 1900 87                         B100 B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZnO 1:2:2 1890 88                         B101 B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZnO 2:9:9 1899 86                         B102 B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZnO 9:45:46 1800 75                       B103 B.sub.2 O.sub.3 W.sub.2 O.sub.5 TiO.sub.2 1:1:1 1910 92                   B104 B.sub.2 O.sub.3 W.sub.2 O.sub.5 TiO.sub.2 1:2:2 1912 91                   B105 B.sub.2 O.sub.3 W.sub.2 O.sub.5 TiO.sub.2 2:9:9 1911 90                   B106 B.sub.2 O.sub.3 W.sub.2 O.sub.5 TiO.sub.2 9:45:46 1811 81                 B107 B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZrO.sub.2 1:1:1 2000 84                   B108 B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZrO.sub.2 1:2:2 2001 86                   B109 B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZrO.sub.2 2:9:9 1998 83                   B110 B.sub.2 O.sub.3 W.sub.2 O.sub.5 ZrO.sub.2 9:45:46 1900 71                 B111 B.sub.2 O.sub.3 W.sub.2 O.sub.5 CdO 1:1:1 1901 87                         B112 B.sub.2 O.sub.3 W.sub.2 O.sub.5 CdO 1:2:2 1910 88                         B113 B.sub.2 O.sub.3 W.sub.2 O.sub.5 CdO 2:9:9 1900 89                         B114 B.sub.2 O.sub.3 W.sub.2 O.sub.5 CdO 9:45:46 1801 79                       B115 B.sub.2 O.sub.3 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 1:1:1 2011 86                                            B116 B.sub.2 O.sub.3 W.sub.2 O.sub.5                                          Al.sub.2 O.sub.3 1:2:2 2009 88                  B117 B.sub.2 O.sub.3 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 2:9:9 2012 85                                            B118 B.sub.2 O.sub.3 W.sub.2 O.sub.5                                          Al.sub.2 O.sub.3 9:45:46 1900 74              __________________________________________________________________________

                                      TABLE 9                                      __________________________________________________________________________          Network-                                                                     forming Modifier Intermediate Molar Discharge Capacity                         Oxide Oxide Oxide Ratio Capacity Maintenance                                  Battery X Y Z X:Y:Z (mAh) (%)                                                __________________________________________________________________________     B119 B.sub.2 O.sub.3                                                                      MoO.sub.2                                                                            PbO   1:1:1                                                                               1901 91                                              B120 B.sub.2 O.sub.3 MoO.sub.2 PbO 1:2:2 1900 92                               B121 B.sub.2 O.sub.3 MoO.sub.2 PbO 2:9:9 1899 90                               B122 B.sub.2 O.sub.3 MoO.sub.2 PbO 9:45:46 1800 80                             B123 B.sub.2 O.sub.3 MoO.sub.2 ZnO 1:1:1 1845 87                               B124 B.sub.2 O.sub.3 MoO.sub.2 ZnO 1:2:2 1850 88                               B125 B.sub.2 O.sub.3 MoO.sub.2 ZnO 2:9:9 1840 89                               B126 B.sub.2 O.sub.3 MoO.sub.2 ZnO 9:45:46 1720 79                             B127 B.sub.2 O.sub.3 MoO.sub.2 TiO.sub.2 1:1:1 1862 91                         B128 B.sub.2 O.sub.3 MoO.sub.2 TiO.sub.2 1:2:2 1857 90                         B129 B.sub.2 O.sub.3 MoO.sub.2 TiO.sub.2 2:9:9 1860 89                         B130 B.sub.2 O.sub.3 MoO.sub.2 TiO.sub.2 9:45:46 1750 79                       B131 B.sub.2 O.sub.3 MoO.sub.2 ZrO.sub.2 1:1:1 1961 86                         B132 B.sub.2 O.sub.3 MoO.sub.2 ZrO.sub.2 1:2:2 1955 85                         B133 B.sub.2 O.sub.3 MoO.sub.2 ZrO.sub.2 2:9:9 1965 86                         B134 B.sub.2 O.sub.3 MoO.sub.2 ZrO.sub.2 9:45:46 1855 75                       B135 B.sub.2 O.sub.3 MoO.sub.2 CdO 1:1:1 1831 88                               B136 B.sub.2 O.sub.3 MoO.sub.2 CdO 1:2:2 1835 86                               B137 B.sub.2 O.sub.3 MoO.sub.2 CdO 2:9:9 1832 85                               B138 B.sub.2 O.sub.3 MoO.sub.2 CdO 9:45:46 1732 73                             B139 B.sub.2 O.sub.3 MoO.sub.2 Al.sub.2 O.sub.3 1:1:1 2001 86                  B140 B.sub.2 O.sub.3 MoO.sub.2 Al.sub.2 O.sub.3 1:2:2 2005 88                  B141 B.sub.2 O.sub.3 MoO.sub.2 Al.sub.2 O.sub.3 2:9:9 2000 85                  B142 B.sub.2 O.sub.3 MoO.sub.2 Al.sub.2 O.sub.3 9:45:46 1900 73              __________________________________________________________________________

                                      TABLE 10                                     __________________________________________________________________________          Network-                                                                     forming Modifier Intermediate Molar Discharge Capacity                         Oxide Oxide Oxide Ratio Capacity Maintenance                                  Battery X Y Z X:Y:Z (mAh) (%)                                                __________________________________________________________________________     B143 B.sub.2 O.sub.3                                                                      Bi.sub.2 O.sub.3                                                                     PbO   1:1:1                                                                               1911 91                                              B144 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 PbO 1:2:2 1905 90                        B145 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 PbO 2:9:9 1909 89                        B146 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 PbO 9:45:46 1812 79                      B147 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZnO 1:1:1 1865 87                        B148 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZnO 1:2:2 1863 86                        B149 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZnO 2:9:9 1862 88                        B150 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZnO 9:45:46 1765 75                      B151 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 TiO.sub.2 1:1:1 1882 92                  B152 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 TiO.sub.2 1:2:2 1879 91                  B153 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 TiO.sub.2 2:9:9 1881 90                  B154 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 TiO.sub.2 9:45:46 1782 80                                                B155 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3                                         ZrO.sub.2 1:1:1 1901 84                         B156 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZrO.sub.2 1:2:2 1899 85                  B157 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZrO.sub.2 2:9:9 1895 83                  B158 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 ZrO.sub.2 9:45:46 1794 70                                                B159 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3                                         CdO 1:1:1 1872 87                               B160 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 CdO 1:2:2 1871 88                        B161 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 CdO 2:9:9 1875 89                        B162 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 CdO 9:45:46 1773 76                      B163 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 Al.sub.2 O.sub.3 1:1:1 2021 88                                           B164 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3                                         Al.sub.2 O.sub.3 1:2:2 2017 89                  B165 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3 Al.sub.2 O.sub.3 2:9:9 2021 86                                           B166 B.sub.2 O.sub.3 Bi.sub.2 O.sub.3                                         Al.sub.2 O.sub.3 9:45:46 1900 73              __________________________________________________________________________

From Tables 6 to 10, it is seen that, in the second battery, the proportion of the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole per mole part of B₂ O₃ should preferably be not higher than 9 mole parts.

Experiment 6

In this experiment, comparative batteries BC39 to BC44 in which the lithium ion-occlusion material was an amorphous material consisting of GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ (each being a network-forming oxide) were fabricated and each of these batteries was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Comparative batteries BC39 to BC44 were fabricated in the same manner as in the fabrication of first battery A1 except that GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ was used in lieu of B₂ O₃ in the preparation of the negative electrode.

Each battery was subjected to charge-discharge cycle testing under the same conditions as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results are shown in Table 11.

                  TABLE 11                                                         ______________________________________                                                 Network-      Discharge                                                                               Capacity                                           forming Capacity Maintenance                                                  Battery Oxide (mAh) (%)                                                      ______________________________________                                         BC39    GeO.sub.2     1500     7                                                 BC40 SiO.sub.2 1650 10                                                         BC41 P.sub.2 O.sub.5 500 3                                                     BC42 As.sub.2 O.sub.3 300 8                                                    BC43 Sb.sub.2 O.sub.3 700 2                                                    BC44 V.sub.2 O.sub.5 1000 9                                                  ______________________________________                                    

As shown in Table 11, comparative batteries BC39 to BC44 were much smaller in discharge capacity and capacity maintenance as compared with first battery A1. This fact indicates that even if an amorphous material comprising GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ is used as the lithium ion-occlusion material in lieu of the amorphous material comprising B₂ O₃ in the first battery, lithium secondary batteries having good characteristics can never be obtained.

Experiment 7

In this experiment, comparative batteries BC45 to BC128 in which the lithium ion-occlusion material was an amorphous material composed of GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ and a modifier oxide were fabricated and each of these batteries was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Comparative batteries BC45 to BC128 were fabricated in the same manner as in the fabrication of second batteries B1 to B14 except that, in the negative electrode preparation, GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ was used in lieu of B₂ O₃.

Each battery was subjected to charge-discharge cycle testing under the same conditions as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results are shown in Tables 12, 13 and 14.

                  TABLE 12                                                         ______________________________________                                                  Network-           Discharge                                                                               Capacity                                     forming Modifier Capacity Maintenance                                         Battery Oxide Oxide (mAh) (%)                                                ______________________________________                                         BC45     GeO.sub.2 Sc.sub.2 O.sub.3                                                                        1500      5                                          BC46 GeO.sub.2 La.sub.2 O.sub.3 1540 12                                        BC47 GeO.sub.2 Y.sub.2 O.sub.3 1550 10                                         BC48 GeO.sub.2 MgO 1570  6                                                     BC49 GeO.sub.2 Li.sub.2 O 1550 15                                              BC50 GeO.sub.2 BaO 1560 12                                                     BC51 GeO.sub.2 CaO 1520 11                                                     BC52 GeO.sub.2 SrO 1490 14                                                     BC53 GeO.sub.2 Na.sub.2 O 1470 13                                              BC54 GeO.sub.2 K.sub.2 O 1450  5                                               BC55 GeO.sub.2 MoO.sub.2 1510 13                                               BC56 GeO.sub.2 WO.sub.3 1530 12                                                BC57 GeO.sub.2 W.sub.2 O.sub.5 1530  8                                         BC58 GeO.sub.2 Bi.sub.2 O.sub.3 1570  6                                        BC59 SiO.sub.2 Sc.sub.2 O.sub.3 1550  8                                        BC60 SiO.sub.2 La.sub.2 O.sub.3 1590 15                                        BC61 SiO.sub.2 Y.sub.2 O.sub.3 1600 13                                         BC62 SiO.sub.2 MgO 1620  9                                                     BC63 SiO.sub.2 Li.sub.2 O 1600 18                                              BC64 SiO.sub.2 BaO 1610 15                                                     BC65 SiO.sub.2 CaO 1570 14                                                     BC66 SiO.sub.2 SrO 1540 17                                                     BC67 SiO.sub.2 Na.sub.2 O 1520 16                                              BC68 SiO.sub.2 K.sub.2 O 1500  8                                               BC69 SiO.sub.2 MoO.sub.2 1560 16                                               BC70 SiO.sub.2 WO.sub.3 1580 15                                                BC71 SiO.sub.2 W.sub.2 O.sub.5 1580 11                                         BC72 SiO.sub.2 Bi.sub.2 O.sub.3 1620  9                                      ______________________________________                                    

                  TABLE 13                                                         ______________________________________                                                  Network-           Discharge                                                                               Capacity                                     forming Modifier Capacity Maintenance                                         Battery Oxide Oxide (mAh) (%)                                                ______________________________________                                         BC73     P.sub.2 O.sub.5                                                                          Sc.sub.2 O.sub.3                                                                        550       1                                          BC74 P.sub.2 O.sub.5 La.sub.2 O.sub.3 640  8                                   BC75 P.sub.2 O.sub.5 Y.sub.2 O.sub.3 650  6                                    BC76 P.sub.2 O.sub.5 MgO 670  2                                                BC77 P.sub.2 O.sub.5 Li.sub.2 O 650 11                                         BC78 P.sub.2 O.sub.5 BaO 660  8                                                BC79 P.sub.2 O.sub.5 CaO 620  7                                                BC80 P.sub.2 O.sub.5 SrO 590 10                                                BC81 P.sub.2 O.sub.5 Na.sub.2 O 570  9                                         BC82 P.sub.2 O.sub.5 K.sub.2 O 550  1                                          BC83 P.sub.2 O.sub.5 MoO.sub.2 610  9                                          BC84 P.sub.2 O.sub.5 WO.sub.3 630  8                                           BC85 P.sub.2 O.sub.5 W.sub.2 O.sub.5 630  4                                    BC86 P.sub.2 O.sub.5 Bi.sub.2 O.sub.3 670  2                                   BC87 As.sub.2 O.sub.3 Sc.sub.2 O.sub.3 300  6                                  BC88 As.sub.2 O.sub.3 La.sub.2 O.sub.3 340 13                                  BC89 As.sub.2 O.sub.3 Y.sub.2 O.sub.3 350 11                                   BC90 As.sub.2 O.sub.3 MgO 370  7                                               BC91 As.sub.2 O.sub.3 Li.sub.2 O 350 16                                        BC92 As.sub.2 O.sub.3 BaO 360 13                                               BC93 As.sub.2 O.sub.3 CaO 320 12                                               BC94 As.sub.2 O.sub.3 SrO 290 15                                               BC95 As.sub.2 O.sub.3 Na.sub.2 O 270 14                                        BC96 As.sub.2 O.sub.3 K.sub.2 O 250  6                                         BC97 As.sub.2 O.sub.3 MoO.sub.2 310 14                                         BC98 As.sub.2 O.sub.3 WO.sub.3 330 13                                          BC99 As.sub.2 O.sub.3 W.sub.2 O.sub.5 330  9                                    BC100 As.sub.2 O.sub.3 Bi.sub.2 O.sub.3 370  7                              ______________________________________                                    

                  TABLE 14                                                         ______________________________________                                                  Network-           Discharge                                                                               Capacity                                     forming Modifier Capacity Maintenance                                         Battery Oxide Oxide (mAh) (%)                                                ______________________________________                                         BC101    Sb.sub.2 O.sub.3                                                                         Sc.sub.2 O.sub.3                                                                        600       1                                          BC102 Sb.sub.2 O.sub.3 La.sub.2 O.sub.3 640  7                                 BC103 Sb.sub.2 O.sub.3 Y.sub.2 O.sub.3 650  5                                  BC104 Sb.sub.2 O.sub.3 MgO 670  1                                              BC105 Sb.sub.2 O.sub.3 Li.sub.2 O 650 10                                       BC106 Sb.sub.2 O.sub.3 BaO 660  7                                              BC107 Sb.sub.2 O.sub.3 CaO 620  6                                              BC108 Sb.sub.2 O.sub.3 SrO 590  9                                              BC109 Sb.sub.2 O.sub.3 Na.sub.2 O 570  8                                       BC110 Sb.sub.2 O.sub.3 K.sub.2 O 550  1                                        BC111 Sb.sub.2 O.sub.3 MoO.sub.2 610  8                                        BC112 Sb.sub.2 O.sub.3 WO.sub.3 630  7                                         BC113 Sb.sub.2 O.sub.3 W.sub.2 O.sub.5 630  3                                  BC114 Sb.sub.2 O.sub.3 Bi.sub.2 O.sub.3 670  1                                 BC115 V.sub.2 O.sub.5 Sc.sub.2 O.sub.3 900  6                                  BC116 V.sub.2 O.sub.5 La.sub.2 O.sub.3 940 13                                  BC117 V.sub.2 O.sub.5 Y.sub.2 O.sub.3 950 11                                   BC118 V.sub.2 O.sub.5 MgO 970  7                                               BC119 V.sub.2 O.sub.5 Li.sub.2 O 950 16                                        BC120 V.sub.2 O.sub.5 BaO 960 13                                               BC121 V.sub.2 O.sub.5 CaO 920 12                                               BC122 V.sub.2 O.sub.5 SrO 890 15                                               BC123 V.sub.2 O.sub.5 Na.sub.2 O 870 14                                        BC124 V.sub.2 O.sub.5 K.sub.2 O 850  6                                         BC125 V.sub.2 O.sub.5 MoO.sub.2 910 14                                         BC126 V.sub.2 O.sub.5 WO.sub.3 930 13                                          BC127 V.sub.2 O.sub.5 W.sub.2 O.sub.5 930  9                                   BC128 V.sub.2 O.sub.5 Bi.sub.2 O.sub.3 970  7                                ______________________________________                                    

As shown in Tables 12 to 14, comparative batteries BC45 to BC128 were much smaller in discharge capacity and capacity maintenance as compared with second batteries B1 to B14. This fact indicates that even if an amorphous material composed of GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ and a modifier oxide is used as the lithium ion-occlusion material in lieu the amorphous material composed of B20, and a modifier oxide in the second battery, lithium secondary batteries having good characteristics can never be obtained.

Experiment 8

In this experiment, comparative batteries BC129 to BC164 in which the lithium ion-occlusion material was an amorphous material composed of GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ and an intermediate oxide were fabricated and each of these batteries was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Comparative batteries BC129 to BC164 were fabricated in the same manner as in the fabrication of second batteries B15 to B20 except that, in the preparation of the negative electrode, GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ was used in lieu of B20.

Each battery was subjected to charge-discharge cycle testing under the same conditions as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results are shown in Tables 15 and 16.

                  TABLE 15                                                         ______________________________________                                                Network-             Discharge                                                                             Capacity                                       forming Intermediate Capacity Maintenance                                     Battery Oxide Oxide (mAh) (%)                                                ______________________________________                                         BC129  SiO.sub.2 PbO        1550    8                                            BC130 SiO.sub.2 ZnO 1590 15                                                    BC131 SiO.sub.2 TiO.sub.2 1600 13                                              BC132 SiO.sub.2 ZrO.sub.2 1620  9                                              BC133 SiO.sub.2 CdO 1600 18                                                    BC134 SiO.sub.2 Al.sub.2 O.sub.3 1610 15                                       BC135 GeO.sub.2 PbO 1400  5                                                    BC136 GeO.sub.2 ZnO 1440 12                                                    BC137 GeO.sub.2 TiO.sub.2 1450 10                                              BC138 GeO.sub.2 ZrO.sub.2 1470  6                                              BC139 GeO.sub.2 CdO 1450 15                                                    BC140 GeO.sub.2 Al.sub.2 O.sub.3 1460 12                                       BC141 P.sub.2 O.sub.5 PbO  400  1                                              BC142 P.sub.2 O.sub.5 ZnO  440  8                                              BC143 P.sub.2 O.sub.5 TiO.sub.2  450  6                                        BC144 P.sub.2 O.sub.5 ZrO.sub.2  470  2                                        BC145 P.sub.2 O.sub.5 CdO  450 11                                              BC146 P.sub.2 O.sub.5 Al.sub.2 O.sub.3  460  8                               ______________________________________                                    

                  TABLE 16                                                         ______________________________________                                                Network-             Discharge                                                                             Capacity                                       forming Intermediate Capacity Maintenance                                     Battery Oxide Oxide (mAh) (%)                                                ______________________________________                                         BC147  As.sub.2 O.sub.3                                                                         PbO        200     6                                            BC148 As.sub.2 O.sub.2 ZnO 240 13                                              BC149 As.sub.2 O.sub.2 TiO.sub.2 250 11                                        BC150 As.sub.2 O.sub.2 ZrO.sub.2 270  7                                        BC151 As.sub.2 O.sub.2 CdO 250 16                                              BC152 As.sub.2 O.sub.3 Al.sub.2 O.sub.3 260 13                                 BC153 Sb.sub.2 O.sub.3 PbO 600  1                                              BC154 Sb.sub.2 O.sub.3 ZnO 640  7                                              BC155 Sb.sub.2 O.sub.3 TiO.sub.2 650  5                                        BC156 Sb.sub.2 O.sub.3 ZrO.sub.2 670  1                                        BC157 Sb.sub.2 O.sub.3 CdO 650 10                                              BC158 Sb.sub.2 O.sub.3 Al.sub.2 O.sub.3 660  7                                 BC159 V.sub.2 O.sub.5 PbO 900  7                                               BC160 V.sub.2 O.sub.5 ZnO 940 14                                               BC161 V.sub.2 O.sub.5 TiO.sub.2 950 12                                         BC162 V.sub.2 O.sub.5 ZrO.sub.2 970  8                                         BC163 V.sub.2 O.sub.5 CdO 950 17                                               BC164 V.sub.2 O.sub.5 Al.sub.2 O.sub.3 960 14                                ______________________________________                                    

As shown in Tables 15 and 16, comparative batteries BC129 to BC164 were much smaller in discharge capacity and capacity maintenance as compared with second batteries B15 to B20. This fact indicates that even if an amorphous material composed of GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ and an intermediate oxide is used as the lithium ion-occlusion material in lieu of the amorphous material composed of B203 and an intermediate oxide in the second battery, lithium secondary batteries having good characteristics can never be obtained.

Experiment 9

In this experiment, comparative batteries BC165 to BC195 in which the lithium ion-occlusion material was an amorphous material composed of GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅, a modifier oxide and an intermediate oxide were fabricated and each of these batteries was evaluated for its discharge capacity and charge-discharge cycle characteristics.

Comparative batteries BC165 to BC194 were fabricated in the same manner as in the fabrication of second batteries B21 to B26 except that, in the preparation of the negative electrode, GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅ was used in lieu of B₂ O₃.

Each battery was subjected to charge-discharge cycle testing under the same conditions as in Experiment 1 and the discharge capacity in the first cycle and the capacity maintenance in the 500th cycle were determined for each battery. The results are shown in Tables 17 and 18.

                  TABLE 17                                                         ______________________________________                                               Network-                  Discharge                                                                             Capacity                                   forming Modifier Intermediate Capacity Maintenance                            Battery Oxide Oxide Oxide (mAh) (%)                                          ______________________________________                                         BC165 SiO.sub.2                                                                               W.sub.2 O.sub.5                                                                         PbO     1550    8                                        BC166 SiO.sub.2 W.sub.2 O.sub.5 ZnO 1590 15                                    BC167 SiO.sub.2 W.sub.2 O.sub.5 TiO.sub.2 1600 13                              BC168 SiO.sub.2 W.sub.2 O.sub.5 ZrO.sub.2 1620  9                              BC169 SiO.sub.2 W.sub.2 O.sub.5 CdO 1600 18                                    BC170 SiO.sub.2 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 1610 15                       BC171 GeO.sub.2 W.sub.2 O.sub.5 PbO 1400  5                                    BC172 GeO.sub.2 W.sub.2 O.sub.5 ZnO 1440 12                                    BC173 GeO.sub.2 W.sub.2 O.sub.5 TiO.sub.2 1450 10                              BC174 GeO.sub.2 W.sub.2 O.sub.5 ZrO.sub.2 1470  6                              BC175 GeO.sub.2 W.sub.2 O.sub.5 CdO 1450 15                                    BC176 GeO.sub.2 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 1460 12                     ______________________________________                                    

                  TABLE 18                                                         ______________________________________                                               Network-                  Discharge                                                                             Capacity                                   forming Modifier Intermediate Capacity Maintenance                            Battery Oxide Oxide Oxide (mAh) (%)                                          ______________________________________                                         BC177 P.sub.2 O.sub.5                                                                         W.sub.2 O.sub.5                                                                         PbO     400     1                                        BC178 P.sub.2 O.sub.5 W.sub.2 O.sub.5 ZnO 440  8                               BC179 P.sub.2 O.sub.5 W.sub.2 O.sub.5 TiO.sub.2 450  6                         BC180 P.sub.2 O.sub.5 W.sub.2 O.sub.5 ZrO.sub.2 470  2                         BC181 P.sub.2 O.sub.5 W.sub.2 O.sub.5 CdO 450 11                               BC182 P.sub.2 O.sub.5 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 460  8                  BC183 As.sub.2 O.sub.3 W.sub.2 O.sub.5 PbO 200  6                              BC184 As.sub.2 O.sub.3 W.sub.2 O.sub.5 ZnO 240 13                              BC185 As.sub.2 O.sub.3 W.sub.2 O.sub.5 TiO.sub.2 250 11                        BC186 As.sub.2 O.sub.3 W.sub.2 O.sub.5 ZrO.sub.2 270  7                        BC187 As.sub.2 O.sub.3 W.sub.2 O.sub.5 CdO 250 16                              BC188 As.sub.2 O.sub.3 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 260 13                 BC189 Sb.sub.2 O.sub.3 W.sub.2 O.sub.5 PbO 660  1                              BC190 Sb.sub.2 O.sub.3 W.sub.2 O.sub.5 ZnO 640  7                              BC191 Sb.sub.2 O.sub.3 W.sub.2 O.sub.5 TiO.sub.2 650  5                        BC192 Sb.sub.2 O.sub.3 W.sub.2 O.sub.5 ZrO.sub.2 670  1                        BC193 Sb.sub.2 O.sub.3 W.sub.2 O.sub.5 CdO 650 10                              BC194 Sb.sub.2 O.sub.3 W.sub.2 O.sub.5 Al.sub.2 O.sub.3 660  7               ______________________________________                                    

As shown in Tables 17 and 18, comparative batteries BC165 to BC194 were much smaller in discharge capacity and capacity maintenance as compared with second batteries B21 to B26. This fact indicates that even if an amorphous material composed of GeO₂, SiO₂, P₂ O₅, As₂ O₃, Sb₂ O₃ or V₂ O₅, a modifier oxide and an intermediate oxide is used as the lithium ion-occlusion material in lieu of the amorphous material composed of B₂ O₃, a modifier oxide and an intermediate oxide in the second battery, lithium secondary batteries having good characteristics can never be obtained.

The present invention thus provides lithium secondary batteries having large discharge capacity and good charge-discharge cycle characteristics. 

What is claimed is:
 1. A lithium secondary battery comprising a positive electrode, a negative electrode comprising a lithium ion-occlusion material, and a nonaqueous electrolyte, the lithium ion-occlusion material being an amorphous material consisting essentially of B₂ O₃.
 2. A lithium secondary battery comprising a positive electrode, a negative electrode comprising a lithium ion-occlusion material, and a nonaqueous electrolyte, the lithium ion-occlusion material being an amorphous material consisting essentially of B₂ O₃ and an oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole.
 3. The lithium secondary battery according to claim 2, wherein the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole consists essentially of at least one modifier oxide selected from the group consisting of MoO₂, WO₃, W₂, O₅, Bi₂ O₃, Sc₂ O₃, La₂ O₃, Y₂ O₃, MgO, Li₂ O, BaO, CaO, SrO, Na₂ O and K₂ O.
 4. The lithium secondary battery according to claim 2, wherein the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole consists essentially of at least one intermediate oxide selected from the group consisting of PbO, ZnO, CdO, TiO₂, ZrO₂ and Al₂ O₃.
 5. The lithium secondary battery according to claim 2, wherein the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole consists essentially of at least one modifier oxide selected from the group consisting of MoO₂, WO₃, W₂ O₅, Bi₂ O₃, Sc₂ O₃, La₂ O₃, Y₂ O₃, MgO, Li₂ O, BaO, CaO, SrO, Na₂ O and K₂ O and at least one intermediate oxide selected from the group consisting of PbO, ZnO, CdO, TiO₂, ZrO₂ and Al₂ O₃.
 6. The lithium secondary battery according to claim 2, wherein the amorphous material consists essentially of one mole part of B203 and not more than 9 mole parts of the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole.
 7. A negative electrode for a lithium secondary battery comprising a lithium ion-occlusion material, the lithium ion-occlusion material being an amorphous material consisting essentially of B₂ O₃.
 8. A negative electrode for a lithium secondary battery comprising a lithium ion-occlusion material, the lithium ion-occlusion material being an amorphous material consisting essentially of B₂ O₃ and an oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole.
 9. The negative electrode for a lithium secondary battery according to claim 8, wherein the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole consists essentially of at least one modifier oxide selected from the group consisting of MoO₂, WO₃, W₂ O₅, Bi₂ O₃, Sc₂ O₃, La₂ O₃, Y₂ O₃, MgO, Li₂ O, BaO, CaO, SrO, Na₂ O and K₂ O.
 10. The negative electrode for a lithium secondary battery according to claim 8, wherein the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole consists essentially of at least one intermediate oxide selected from the group consisting of PbO, ZnO, CdO, TiO₂, ZrO₂ and Al₂ O₃.
 11. The negative electrode for a lithium secondary battery according to claim 8, wherein the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole consists essentially of at least one modifier oxide selected from the group consisting of MoO₂, WO₃, W₂ O₅, Bi₂ O₃, Sc₂ O₃, La₂ O₃, Y₂ O₃, MgO, Li₂ O, BaO, CaO, SrO, Na₂ O and K₂ O and at least one intermediate oxide selected from the group consisting of PbO, ZnO, CdO, TiO₂, ZrO₂ and Al₂ O₃.
 12. The negative electrode for a lithium secondary battery according to claim 8, wherein the amorphous material consists essentially of one mole part of B₂ O₃ and not more than 9 mole parts of the oxide whose cation-oxygen bond strength is smaller than 335 kJ/mole. 